Lustre 1.6 Operations Manual

21.7 Lockless I/O Tunables
The lockless I/O tunable feature allows servers to ask clients to do lockless I/O
(liblustre-style where the server does the locking) on contended files.
The lockless I/O patch introduces these tunables:
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OST-side:
/proc/fs/lustre/ldlm/filter-lustre-*
contended_locks - If the number of lock conflicts in the scan of granted and
waiting queues at contended_locks is exceeded, the resource is considered to
be contended.
contention_seconds - The resource keeps itself in a contended state as set in
the parameter.
max_nolock_bytes - Server-side locking set only for requests less than the
blocks set in the max_nolock_bytes parameter. If this tunable is set to zero (0),
it disables server-side locking for read/write requests.
Client-side:
/proc/fs/lustre/llite/lustre-*
contention_seconds - llite inode remembers its contended state for the time
specified in this parameter.
Client-side statistics:
The /proc/fs/lustre/llite/lustre-*/stats file has new rows for
lockless I/O statistics.
lockless_read_bytes and lockless_write_bytes - To count the total
bytes read or written, the client makes its own decisions based on the request
size. The client does not communicate with the server if the request size is
smaller than the min_nolock_size, without acquiring locks by the client.
21.8 Data Checksums
To avoid the risk of data corruption on the network, a Lustre client can perform endto-end
data checksums 1 . Be aware that at high data rates, checksumming can impact
Lustre performance.
1. This feature computes a 32-bit checksum of data read or written on both the client and server, and ensures
that the data has not been corrupted in transit over the network.
21-12 Lustre 1.6 Operations Manual • September 2008